This invention relates to an electroluminescent (EL) device using strontium sulfide (SrS) as a matrix material for the electroluminescent layer and a process for producing the same, and particularly to an electroluminescent device suitable for flat display and a process for producing the same.
Japanese Patent Application Kokai (Laid-open) No. 60-172196 discloses an electroluminescent layer for a thin film electroluminescent device, which comprises zinc sulfide (ZnS) as a matrix material and contains at least one of manganese, copper, silver, magnesium, aluminum and their halides and further contains nitrogen, phosphorus, arsenic or antimony. It is further disclosed that the thin zinc sulfide film is formed by vacuum vapor deposition, or sputtering.
Television Gakai-shi, Vol. 40, No. 10, 991-997, (1986) disclosed vacuum vapor deposition of an electroluminescent layer comprising strontium sulfide (SrS) as a matrix material and containing cerium (Ce) for a thin film electroluminescent device.
The luminescence brightness of the thin film electroluminescent device having an electroluminescent layer comprising ZnS as a matrix material largely depends upon slight differences in the production conditions, as mentioned in said Japanese Patent Application Kokai (Laid-open) No. 60-172196, and it is hard to obtain electroluminescent devices of high luminescence brightness with a good reproducibility.